Wireless power system

ABSTRACT

A wireless power system receives an input voltage signal from a first node of a secondary side coil, comprises an active rectifier, a buck converter, and a linear charger comprising a first resistor, a second resistor, a third resistor, a mode switching circuit, a current mirror circuit. The active rectifier rectifies the input voltage signal to generate a rectified voltage signal. The first resistor couples between a first node point and second node point. The second resistor couples between the second node point and ground terminal. The third resistor couples between a third node point and ground terminal. The current mirror circuit outputs a reference current and charge current according to the rectified voltage signal and mode switching signal generated by the mode switching circuit. The buck converter outputs a first output voltage signal or second output voltage signal according to a first node point voltage.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Taiwan Application Serial Number107116670, filed May 16, 2018, which is herein incorporated by referencein its entirety.

BACKGROUND Field of Invention

The present disclosure relates to a power system. More particularly, thepresent disclosure relates to a wireless power system comprises anactive rectifier, a linear charger, and a buck converter.

Description of Related Art

With the reaches regarding to the medical electronic device accumulates,the categories of the implantable medical electronic device becomes moreand more, such as the pacemaker and the artificial cochlea. The wirelesscharging technology makes the implantable medical electronic device nolonger needs to be charged through the surgery or invasive chargingwire, and thus the quality of life of the patient is significantlyimproved. However, to increase the charging and discharging efficiency,the rectifier circuit, the charging circuit, and the converter circuitof the implantable medical electronic device need to be integrated intoa single chip circuit.

SUMMARY

The disclosure provides a wireless power system. The wireless powersystem is configured to receive an input voltage signal from a firstnode of a secondary side coil, charge a battery module according to theinput voltage signal, and comprise an active rectifier, a linearcharger, and a buck converter. The active rectifier is configured toreceive the input voltage signal, and rectify the input voltage signalto generate a rectified voltage signal. The linear charger comprises afirst resistor, a second resistor, a third resistor, a mode switchingcircuit, and a current mirror circuit. The first resistor is coupledbetween a first node point and a second node point, wherein the batterymodule coupled with the first node point. The second resistor is coupledbetween the second node point and a ground terminal. The third resistoris coupled between a third node point and the ground terminal. The modeswitching circuit is configured to generate a mode switching signalaccording to a second node point voltage of the second node point and athird node point voltage of the third node point. The current mirrorcircuit is configured to output a reference current and a charge currentto the third node point and the first node point, respectively,according to the rectified voltage signal and the mode switching signal.The buck converter is coupled with the first node point, and configuredto selectively output a first output voltage signal or a second outputvoltage signal according to a first node point voltage of the first nodepoint.

It is to be understood that both the foregoing general description andthe following detailed description are by examples, and are intended toprovide further explanation of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be more fully understood by reading the followingdetailed description of the embodiment, with reference made to theaccompanying drawings as follows:

FIG. 1 is a simplified block diagram of a wireless power systemaccording to one embodiment of the present disclosure.

FIG. 2 is a simplified functional block diagram of the linear chargeraccording to one embodiment of the present disclosure.

FIG. 3 is a simplified block diagram of the mode switching circuitaccording to one embodiment of the present disclosure.

FIG. 4 is a simplified functional block diagram of a linear chargeraccording to one embodiment of the present disclosure.

FIG. 5 is a simplified functional block diagram of the active rectifieraccording to one embodiment of the present disclosure.

FIG. 6 is a simplified functional block diagram of an active rectifieraccording to one embodiment of the present disclosure.

FIG. 7 illustrates schematic waveforms according to one operativeembodiment of the active rectifier.

FIG. 8 is a simplified functional block diagram of the buck converteraccording to one embodiment of one present disclosure.

FIG. 9 is a simplified functional block diagram of a buck converteraccording to one embodiment of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments of thedisclosure, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers are used in thedrawings and the description to refer to the same or like parts.

FIG. 1 is a simplified block diagram of a wireless power system 100according to one embodiment of the present disclosure. The wirelesspower system 100 is coupled with a secondary side coil 101 and a batterymodule 103. When a power voltage signal Vs flows through a first sidecoil 105, the secondary side coil 101 may provide an input voltagesignal Vin. The wireless power system 100 is configured to receive theinput voltage signal Vin, and charge the battery module 103 according tothe input voltage signal Vin. The wireless power system 100 comprises anactive rectifier 110, a linear charger 120, and a buck converter 130.For the sake of brevity, other functional blocks of the wireless powersystem 100 are not shown in FIG. 1.

In practice, the battery module 103 may be realized by various suitablelithium batteries. The wireless power system 100, the secondary sidecoil 101, and the battery module 103 is suitable for the implantablemedical electronic device, and capable of cooperatively provide powerfor the implantable medical electronic device.

In addition, the first side coil 105 may be realized by various suitablewireless charging transmitters. When the first side coil 105 is near bythe secondary side coil 101, the charging operation for the batterymodule 103 may be conducted by the cooperation of the first side coil105, the secondary side coil 101, and the wireless power system 100.

The active rectifier 110 is coupled with the first node and second nodeof the secondary side coil 101, and configured to receive the inputvoltage signal Vin from the first node of the secondary side coil 101.The active rectifier 110 is further configured to rectify the inputvoltage signal Vin to generate a rectified voltage signal Vrec. Thelinear charger 120 is coupled between the active rectifier 110 and thefirst node point N1, and configured to receive the rectified voltagesignal Vrec. The linear charger 120 is further configured to output acharge current Ichg to the first node point N1 according to therectified voltage signal Vrec, so as to charge the battery module 103coupled with the first node point N1. The buck converter 130 is coupledwith the first node point N1, and configured to selectively output afirst output voltage signal Vout1 or a second output voltage signalVout2 according to the first node point voltage Vn1 of the first nodepoint N1. The first node point voltage Vn1 may be provided by the linearcharger 120 or battery module 103.

FIG. 2 is a simplified functional block diagram of the linear charger120 according to one embodiment of the present disclosure. The linearcharger 120 comprises a first resistor R1, a second resistor R2, a thirdresistor R3, a mode switching circuit 210, and a current mirror circuit220. The first resistor R1 is coupled between the first node point N1and the second node point N2, the second resistor R2 is coupled betweenthe second node point N2 and the ground terminal, and the third resistorR3 is coupled between the third node point N3 and the ground terminal.The mode switching circuit 210 is coupled with the second node point N2and the third node point N3, and is configured to output the modeswitching signal Sms according to the second node point voltage Vn2 ofthe second node point N2 and the third node point voltage Vn3 of thethird node point N3. The current mirror circuit 220 is configured tooutput the reference current Iref and the charge current Ichg to thethird node point N3 and the first node point N1, respectively, accordingto the rectified voltage signal Vrec and the mode switching signal Sms.

In the embodiment of FIG. 2, the current mirror circuit 220 comprises afirst transistor 222 and a second transistor 224, wherein the widthlength ratio of the second transistor 224 is larger than the widthlength ratio of the first transistor 222. The first node of the firsttransistor 222 is configured to receive the rectified voltage signalVrec, and the second node of the first transistor 222 is coupled withthe third node point N3. The first node of the second transistor 224 isconfigured to receive the rectified voltage signal Vrec, and the secondnode of the second transistor 224 is coupled with the first node pointN1. In addition, the control node of the first transistor 222 and thecontrol node of the second transistor 224 are configured to receive themode switching signal Sms from the mode switching circuit 210.

In practice, the first transistor 222 and the second transistor 224 maybe realized by various suitable P-type transistors.

It is worth mentioning that the current mirror circuit 220 may determineto use a constant current or a constant voltage to charge the batterymodule 103 according to the mode switching signal Sms.

Specifically, the first node point voltage Vn1 and the second node pointvoltage Vn2 may reflect the state of charge of the battery module 103.For example, when the state of charge of the battery module 103 isclosed to 100%, the first node point voltage Vn1 may be 4.2 V and thesecond node point voltage Vn2 may be 1.2 V. When the second node pointvoltage Vn2 is smaller than a predetermined voltage, the mode switchingcircuit 210 may instruct the current mirror circuit 220 to output thereference current Iref and the charge current Ichg, so as to charge thebattery module 103 by the charge current Ichg. In this situation, thecharge current Ichg has a fixed ratio with the reference current Iref.In some embodiment, the ratio of the reference current Iref to thecharge current Ichg may be 1 to 1000.

On the other hand, when the second node point voltage Vn2 is larger thanor equal to the predetermined voltage, the mode switching circuit 210may instruct the current mirror circuit 220 to configure the magnitudeof the charge current Ichg to be approximately negatively correlatedwith the magnitude of the first node point voltage Vn1 or the secondnode point voltage Vn2, so as to charge the battery module 103 by theconstant voltage.

FIG. 3 is a simplified block diagram of the mode switching circuit 210according to one embodiment of the present disclosure. The modeswitching circuit 210 comprises a first operational amplifier 310, asecond operational amplifier 320, a third transistor 330, and the fourthtransistor 340. The first input node of the first operational amplifier310 (e.g., the positive input node) is coupled with the third node pointN3, and the second input node of the first operational amplifier 310(e.g., the negative input node) is configured to receive the firstreference voltage Vref1. The first input node of the second operationalamplifier 320 (e.g., the positive input node) is coupled with the secondnode point N2, and second input node of the second operational amplifier320 (e.g., the negative input node) is configured to receive the firstreference voltage Vref1. The first node of the third transistor 330 iscoupled with the output node of the first operational amplifier 310, andthe control node of the third transistor 330 is coupled with the outputnode of the second operational amplifier 320. The first node of thefourth transistor 340 is coupled with the second node of the thirdtransistor 330, the second node of the fourth transistor 340 is coupledwith the output node of the second operational amplifier 320, and thecontrol node of the fourth transistor 340 is coupled with the outputnode of the first operational amplifier 310. For the sake of brevity,other functional blocks of the mode switching circuit 210 are not shownin FIG. 3.

In practice, the third transistor 330 and fourth transistor 340 may berealized by various suitable P-type transistors.

The operations of the linear charger 120 will be further described inthe following by reference to FIGS. 2 and 3. When the state of charge ofthe battery module 103 is at a lower value (e.g., lower than 95%), thefirst node point voltage Vn1 and the second node point voltage Vn2 wouldboth be lower than the first reference voltage Vref1. Therefore, thefirst operational amplifier 310 and the second operational amplifier 320would output low voltages. In addition, the voltage outputted by thefirst operational amplifier 310 is lower than the voltage outputted bythe second operational amplifier 320. As a result, the third transistor330 may be conducted similarly to a forward biased diode, the fourthtransistor 340 may be switched off similarly to a reverse biased diode,and thus the mode switching circuit 210 would select the output of thefirst operational amplifier 310 as the mode switching signal Sms.

In this situation, the mode switching signal Sms may have a fixedvoltage level. Thus, the current mirror circuit 220 may output thereference current Iref having a fixed value, and output the chargecurrent Ichg having a fixed ratio with the reference current Iref, so asto charge the battery module 103 under a constant current mode.

While the state of charge of the battery module 103 increases, the firstnode point voltage Vn1 and the second node point voltage Vn2 may beincreased with the state of charge of the battery module 103. Thus, thevoltage outputted by the second operational amplifier 320 may also beincreased. When the state of charge of the battery module 103 has ahigher value (e.g., larger than 95%), the voltage outputted by thesecond operational amplifier 320 may be higher than the voltageoutputted by the first operational amplifier 310. As a result, the thirdtransistor 330 may be switched off similarly to the reverse biaseddiode, the fourth transistor 340 may be conducted similarly to a forwardbiased diode, and thus the mode switching circuit 210 would select theoutput of the second operational amplifier 320 as the mode switchingsignal Sms.

In this situation, since the voltage outputted by the second operationalamplifier 320 is increased, the second transistor 224 would be graduallyswitched off, and thus the magnitude of the charge current Ichg would begradually decreased. The magnitude of the charge current Ichg may beapproximately negatively correlated with the magnitude of the first nodepoint voltage Vn1 or the second node point voltage Vn2, so as to chargethe battery module 103 under a constant voltage mode.

FIG. 4 is a simplified functional block diagram of a linear charger 120a according to one embodiment of the present disclosure. The linearcharger 120 a is suitable for the wireless power system 100 and issimilar to the linear charger 120, and the difference is that the linearcharger 120 a further comprises a regulating transistor 410 and aregulating operational amplifier 420. The first node of the regulatingtransistor 410 is coupled with the second node of the first transistor222, and the second node of the regulating transistor 410 is coupledwith the third node point N3. The first input node of the regulatingoperational amplifier 420 (e.g., the positive input node) is coupledwith the first node of the regulating transistor 410, the second inputnode of the regulating operational amplifier 420 (e.g., the negativeinput node) is coupled with the first node point N1, and the output nodeof the regulating operational amplifier 420 is coupled with the controlnode of the regulating transistor 410.

When the linear charger 120 a charges the battery module 103 under theconstant current mode, the regulating transistor 410 and the regulatingoperational amplifier 420 may dynamically regulate the magnitude of thecharge current Ichg. When the magnitude of the charge current Ichg isincreased, for example, the voltage outputted by the regulatingoperational amplifier 420 may be decreased, and thereby making theregulating transistor 410 be gradually switched off. Therefore, themagnitude of the reference current Iref may be gradually decreased, andthe magnitude of the charge current Ichg having the fixed ratio with thereference current Iref may also be decreased. As another example, whenthe magnitude of the charge current Ichg is decreased, the voltageoutputted by the regulating operational amplifier 420 may be increased,and thereby making the regulating transistor 410 be gradually conductedto increase the magnitude of the charge current Ichg.

The foregoing descriptions regarding the implementations, connections,operations, and related advantages of the linear charger 120 are alsoapplicable to the linear charger 120 a. For the sake of brevity, thosedescriptions will not be repeated here.

FIG. 5 is a simplified functional block diagram of the active rectifier110 according to one embodiment of the present disclosure. The activerectifier 110 comprises a fifth transistor 510, a sixth transistor 520,a seventh transistor 530, an eighth transistor 540, a control circuit550, a first capacitor C1, and a second capacitor C2. The first node ofthe fifth transistor 510 is configured to provide the rectified voltagesignal Vrec. The second node of the fifth transistor 510 is coupled withthe first node of the secondary side coil 101 through the fourth nodepoint N4, and is configured to receive the input voltage signal Vin. Thefirst node of the sixth transistor 520 is configured to provide therectified voltage signal Vrec, the second node of the sixth transistor520 is coupled with the control node of the fifth transistor 510, and iscoupled with the second node of the secondary side coil 101 through thefifth node point N5. The control node of the sixth transistor 520 iscoupled with the second node of the fifth transistor 510. The first nodeof the seventh transistor 530 is coupled with the fourth node point N4,and the second node of the seventh transistor 530 is coupled with theground terminal. The first node of the eighth transistor 540 is coupledwith the fifth node point N5, and the second node of the eighthtransistor 540 is coupled with the ground terminal. The first node ofthe first capacitor C1 is configured to receive the rectified voltagesignal Vrec, and the second node of the first capacitor C1 is coupledwith the sixth node point N6. The second capacitor C2 is coupled betweenthe sixth node point N6 and the ground terminal.

The control circuit 550 comprises a first comparator 552 and a secondcomparator 554. The first input node of the first comparator 552 (e.g.,the positive input node) is coupled with the ground terminal, the secondinput node of the first comparator 552 (e.g., the negative input node)is coupled with the fourth node point N4, and the output node of thefirst comparator 552 is coupled with the control node of the seventhtransistor 530. The first input node of the second comparator 554 (e.g.,the positive input node) is coupled with the ground terminal, the secondinput node of the second comparator 554 (e.g., the negative input node)is coupled with the fifth node point N5, and the output node of thesecond comparator 554 is coupled with the control node of the eighthtransistor 540.

In practice, the fifth transistor 510 and the sixth transistor 520 maybe realized by various suitable P-type transistors. The seventhtransistor 530 and the eighth transistor 540 may be realized by varioussuitable N-type transistors.

When a corresponding current of the input voltage signal Vin flows fromthe first node of the secondary side coil 101 to the fourth node pointN4, a fourth node voltage Vn4 of the fourth node point N4 would behigher than a fifth node voltage Vn5 of the fifth node point N5. Thus,the fifth transistor 510 may be conducted and the sixth transistor 520may be switched off, and thereby making the input voltage signal Vin betransmitted to the aforesaid linear charger 120 through the fifthtransistor 510, and also transmitted to the ground terminal through thefirst capacitor C1 and the second capacitor C2.

In this situation, the fourth node voltage Vn4 would be higher than theground voltage of the ground terminal, and the fifth node point N5 wouldbe lower than the ground voltage. Thus, the first comparator 552 mayoutput a low voltage to switch off the seventh transistor 530, and thesecond comparator 554 may output a high voltage to conduct the eighthtransistor 540.

On the contrary, when the corresponding current of the input voltagesignal Vin flows from the second node of the secondary side coil 101 tothe fifth node point N5, the fifth node point N5 may be higher than thefourth node voltage Vn4. In this situation, the fifth transistor 510 andthe eighth transistor 540 may be switched off, and the sixth transistor520 and the seventh transistor 530 may be conducted. Therefore, theinput voltage signal Vin may be transmitted to the aforesaid linearcharger 120 through the sixth transistor 520.

FIG. 6 is a simplified functional block diagram of an active rectifier110 a according to one embodiment of the present disclosure. The activerectifier 110 a is similar to the active rectifier 110, the differenceis that the active rectifier 110 a further comprises a ninth transistor610, a tenth transistor 620, an eleventh transistor 630, a twelfthtransistor 640, and a control circuit 650. The first node of the ninthtransistor 610 is coupled with the second node of the fifth transistor510, and the second node of the ninth transistor 610 is coupled with thefourth node point N4. The first node of the tenth transistor 620 iscoupled with the second node of the sixth transistor 520, and the secondnode of the tenth transistor 620 is coupled with the fifth node pointN5. The first node of the eleventh transistor 630 is coupled with thefourth node point N4, the second node of the eleventh transistor 630 iscoupled with the first node of the seventh transistor 530. The firstnode of the twelfth transistor 640 is coupled with the fifth node pointN5, and the second node of the twelfth transistor 640 is coupled withthe first node of the eighth transistor 540. In addition, the controlnode of the ninth transistor 610, the control node of the tenthtransistor 620, the control node of the eleventh transistor 630, and thecontrol node of the twelfth transistor 640 are coupled with the sixthnode point N6.

In practice, the ninth transistor 610 and the tenth transistor 620 maybe realized by various suitable P-type transistors. The eleventhtransistor 630 and the twelfth transistor 640 may be realized by varioussuitable N-type transistors.

In this embodiment, the capacitance of the first capacitor C1 isapproximately equal to the capacitance of the second capacitor C2, andthereby making the magnitude of the sixth node point voltage Vn6 of thesixth node point N6 approximately equal to half of the magnitude of therectified voltage signal Vrec. As a result, when the correspondingcurrent of the input voltage signal Vin flows from the first node ofsecondary side coil 101 to the fourth node point N4, the fifthtransistor 510, the eighth transistor 540, the ninth transistor 610, andthe twelfth transistor 640 would be conducted, and the sixth transistor520, the seventh transistor 530, the tenth transistor 620, and theeleventh transistor 630 would be switched off. When the correspondingcurrent of the input voltage signal Vin flows from the second node ofthe secondary side coil 101 to the fifth node point N5, the fifthtransistor 510, the eighth transistor 540, the ninth transistor 610, andthe twelfth transistor 640 may be switched off, and the sixth transistor520, the seventh transistor 530, the tenth transistor 620, and theeleventh transistor 630 would be conducted.

The voltage difference between the first node of the fifth transistor510 and the fourth node point N4 would be allocated to the fifthtransistor 510 and ninth transistor 610 coupled in a series connection.Therefore, the fifth transistor 510 and the ninth transistor 610 can beprevented from being damaged by the too large drain-to-source voltage.Similarly, the sixth transistor 520 and tenth transistor 620 coupled inthe series connection, the seventh transistor 530 and eleventhtransistor 630 coupled in the series connection, and the eighthtransistor 540 and twelfth transistor 640 coupled in the seriesconnection are capable of preventing the adjacent transistor from beingdamaged by the too large drain-to-source voltage.

In addition, since the seventh transistor 530 and eighth transistor 540having larger width length ratios, the seventh transistor 530 and theeighth transistor 540 would have larger gate parasitic capacitors.Therefore, multiple buffer amplifiers (not shown in FIG. 6) may becoupled in the series connection between the seventh transistor 530 andfirst comparator 552, and between the eighth transistor 540 and thesecond comparator 554. However, the multiple buffer amplifiers coupledin the series connection may cause the seventh transistor 530 and theeighth transistor 540 facing the problem of conduction delay and switchoff delay. As a result, the conversion efficiency of the activerectifier 110 may decrease, and the current may reversely flow from thefourth node point N4 or the fifth node point N5 to the ground terminal.

To overcome the aforesaid problems, the control circuit 650 not onlycomprises the first comparator 552 and the second comparator 554, butalso comprises a first adder AD1, a second adder AD2, and a compensationcircuit 652. The first adder AD1 is coupled with the second input nodeof the first comparator 552, and the second adder AD2 is coupled withthe second input node of the second comparator 554. The compensationcircuit 652 is coupled with the first adder AD1 and second adder AD2,and is configured to output a first compensation signal Vcmp1 and asecond compensation signal Vcmp2 to the first adder AD1 and the secondadder AD2, respectively.

As shown in FIG. 7, with respect to the first comparator 552 and thefirst adder AD1, during a first time period T1, the seventh transistor530 may be switched from the switch-off state to the conducted state. Inthis situation, the compensation circuit 652 may output the firstcompensation signal Vcmp1 having a first voltage level V1 to first adderAD1, so as to pull down the voltage level of the second input node ofthe first comparator 552. As a result, the time point that the firstcomparator 552 outputs the high voltage would be moved forward toconduct the seventh transistor 530 earlier.

In addition, during a second time period P2, the seventh transistor 530may be switched from the conducted state to the switch-off state. Inthis situation, the compensation circuit 652 may output the firstcompensation signal Vcmp1 having a second voltage level V2 to the firstadder AD1, so as to raise up the voltage level of the second input nodeof the first comparator 552. As a result, the time point that the firstcomparator 552 outputs the low voltage would be moved forward to switchoff the seventh transistor 530 earlier, wherein the second voltage levelV2 is higher than the first voltage level V1.

Similarly, when the eighth transistor 540 is switched from theswitch-off state to the conducted state, the compensation circuit 652may output the second compensation signal Vcmp2 having a third voltagelevel to the second adder AD2, so as to pull down the voltage level ofthe second input node of the second comparator 554. As a result, thetime point that the second comparator 554 outputs the high voltage wouldbe moved forward to conduct the eighth transistor 540 earlier. When theeighth transistor 540 is switched from the conducted state to theswitch-off state, the compensation circuit 652 may output the secondcompensation signal Vcmp2 having a fourth voltage level to the secondadder AD2, so as to raise up the voltage level of the second input nodeof the second comparator 554. As a result, the time point that thesecond comparator 554 outputs the low voltage would be moved forward toswitch off the eighth transistor 540 earlier, wherein the fourth voltagelevel V4 is higher than the third voltage level.

The foregoing descriptions regarding the implementations, connections,operations, and related advantages of the active rectifier 110 are alsoapplicable to the active rectifier 110 a. For the sake of brevity, thosedescriptions will not be repeated here.

FIG. 8 is a simplified functional block diagram of the buck converter130 according to one embodiment of one present disclosure. The buckconverter 130 comprises a thirteenth transistor 810, a fourteenthtransistor 820, a fifteenth transistor 830, a sixteenth transistor 840,a seventeenth transistor 850, and an inductor 860. The first node of thethirteenth transistor 810 is coupled with the first node point N1, thesecond node of the thirteenth transistor 810 is coupled with the seventhnode point N7, and the control node of the thirteenth transistor 810 isconfigured to receive the first switch signal SW1. The first node of thefourteenth transistor 820 is coupled with the seventh node point N7, thesecond node of the fourteenth transistor 820 is coupled with the groundterminal, and the control node of the fourteenth transistor 820 isconfigured to receive the second switch signal SW2. The first node ofthe fifteenth transistor 830 is coupled with the eighth node point N8,the second node of the fifteenth transistor 830 is configured to providethe first output voltage signal Vout1, and the control node of thefifteenth transistor is configured to receive the third switch signalSW3. The first node of the sixteenth transistor 840 is coupled with theeighth node point N8, the second node of the sixteenth transistor 840 isconfigured to provide the second output voltage signal Vout2, and thecontrol node of the sixteenth transistor 840 is configured to receivethe fourth switch signal SW4. The first node of the seventeenthtransistor 850 is coupled with the eighth node point N8, the second nodeof the seventeenth transistor 850 is coupled with the ground terminal,and the control node of the seventeenth transistor 850 is configured toreceive the fifth switch signal SW5. The inductor 860 is coupled betweenthe seventh node point N7 and the eighth node point N8.

In practice, the thirteenth transistor 810, the fifteenth transistor830, and the sixteenth transistor 840 may be realized by varioussuitable P-type transistors. The fourteenth transistor 820 and theseventeenth transistor 850 may be realized by various suitable N-typetransistors.

When the buck converter 130 outputs the first output voltage signalVout1 and does not output the second output voltage signal Vout2, thethirteenth transistor 810 and the fourteenth transistor 820 would bealternatively conducted and switched off, the fifteenth transistor 830and the seventeenth transistor 850 would also be alternatively conductedand switched off. In addition, the sixteenth transistor 840 ismaintained at the switch-off state.

On the other hand, when the buck converter 130 does not output the firstoutput voltage signal Vout1 and outputs the second output voltage signalVout2, the thirteenth transistor 810 and the fourteenth transistor 820would be alternatively conducted and switched off, the sixteenthtransistor 840 and the seventeenth transistor 850 would also bealternatively conducted and switched off. In addition, the fifteenthtransistor 830 is maintained at the switch-off state.

In practice, the third switch signal SW3 and the fourth switch signalSW4 may be two pulse width modulation (PWM) signals that have differentduty ratios, so as to configure the first output voltage signal Vout1and the second output voltage signal Vout2 to have different voltagelevels.

FIG. 9 is a simplified functional block diagram of a buck converter 130a according to one embodiment of the present disclosure. The buckconverter 130 a is suitable for the wireless power system 100 andsimilar to the buck converter 130, the difference is that the buckconverter 130 a further comprises an eighteenth transistor 910 and anineteenth transistor 920. The first node of the eighteenth transistor910 is coupled with the second node of the thirteenth transistor 810,and the second node of the eighteenth transistor 910 is coupled with theseventh node point N7. The first node of the nineteenth transistor 920is coupled with the seventh node point N7, and the second node of thenineteenth transistor 920 is coupled with the first node of thefourteenth transistor 820.

In practice, the eighteenth transistor 910 can be realized by varioussuitable P-type transistors. The nineteenth transistor 920 can berealized by various suitable N-type transistors.

The control node of the eighteenth transistor 910 and the control nodeof the nineteenth transistor 920 are configured to receive the secondreference voltage Vref2, wherein the magnitude of the second referencevoltage Vref2 is approximately equal to half of the magnitude of thefirst node point voltage Vn1. Therefore, while the thirteenth transistor810 is conducted, the eighteenth transistor 910 is also conducted, andwhile the fourteenth transistor 820 is conducted, the nineteenthtransistor 920 is also conducted.

As a result, the voltage difference between the first node of thethirteenth transistor 810 and the seventh node point N7 would beallocated to the thirteenth transistor 810 and the eighteenth transistor910. Therefore, the thirteenth transistor 810 and the eighteenthtransistor 910 can be prevented from being damaged by the too largedrain-to-source voltage. Similarly, the voltage difference between theseventh node point N7 and the ground terminal would be allocated to thefourteenth transistor 820 and the nineteenth transistor 920. Therefore,the fourteenth transistor 820 and the nineteenth transistor 920 can beprevented from being damaged by the too large drain-to-source voltage.

As can be appreciated from the foregoing descriptions, the components ofthe wireless power system 100 are all compatible with the semiconductorfabrication process, and thus the wireless power system 100 may berealized by a single system-on-chip (SoC) circuit. As a result, thewireless power system 100 can provide high charging and dischargingefficiency.

Certain terms are used throughout the description and the claims torefer to particular components. One skilled in the art appreciates thata component may be referred to as different names. This disclosure doesnot intend to distinguish between components that differ in name but notin function. In the description and in the claims, the term “comprise”is used in an open-ended fashion, and thus should be interpreted to mean“include, but not limited to.” The term “couple” is intended to compassany indirect or direct connection. Accordingly, if this disclosurementioned that a first device is coupled with a second device, it meansthat the first device may be directly or indirectly connected to thesecond device through electrical connections, wireless communications,optical communications, or other signal connections with/without otherintermediate devices or connection means.

The term “voltage signal” used throughout the description and the claimsmay be expressed in the format of a current in implementations, and theterm “current signal” used throughout the description and the claims maybe expressed in the format of a voltage in implementations.

In addition, the singular forms “a,” “an,” and “the” herein are intendedto comprise the plural forms as well, unless the context clearlyindicates otherwise.

Although the present disclosure has been described in considerabledetail with reference to certain embodiments thereof, other embodimentsare possible. Therefore, the spirit and scope of the appended claimsshould not be limited to the description of the embodiments containedherein.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentdisclosure without departing from the scope or spirit of the disclosure.In view of the foregoing, it is intended that the present disclosurecover modifications and variations of this disclosure provided they fallwithin the scope of the following claims.

What is claimed is:
 1. A wireless power system, configured to receive an input voltage signal from a first node of a secondary side coil, and charge a battery module according to the input voltage signal, comprising: an active rectifier, configured to receive the input voltage signal, and rectify the input voltage signal to generate a rectified voltage signal; a linear charger, comprising: a first resistor, coupled between a first node point and a second node point, wherein the battery module coupled with the first node point; a second resistor, coupled between the second node point and a ground terminal; a third resistor, coupled between a third node point and the ground terminal; a mode switching circuit, configured to generate a mode switching signal according to a second node point voltage of the second node point and a third node point voltage of the third node point; and a current mirror circuit, configured to output a reference current and a charge current to the third node point and the first node point, respectively, according to the rectified voltage signal and the mode switching signal; and a buck converter, coupled with the first node point, and configured to selectively output a first output voltage signal or a second output voltage signal according to a first node point voltage of the first node point, wherein the mode switching circuit comprises: a first operational amplifier, comprising a first input node, a second input node, and an output node, wherein the first input node of the first operational amplifier is coupled with the third node point, and the second input node of the first operational amplifier is configured to receive a first reference voltage; a second operational amplifier, comprising a first input node, a second input node, and an output node, wherein the first input node of the second operational amplifier is coupled with the second node point, and the second input node of the second operational amplifier is configured to receive the first reference voltage; a third transistor, comprising a first node, a second node, and a control node, wherein the first node of the third transistor is coupled with the output node of the first operational amplifier, and the control node of the third transistor is coupled with the output node of the second operational amplifier; and a fourth transistor, comprising a first node, a second node, and a control node, wherein the first node of the fourth transistor is coupled with the second node of the third transistor, the second node of the fourth transistor is coupled with the output node of the second operational amplifier, and the control node of the fourth transistor is coupled with the output node of the first operational amplifier.
 2. The wireless power system of claim 1, wherein when the second node point voltage is smaller than a predetermined voltage, the charge current has a fixed ratio with the reference current, and when the second node point voltage is larger than or equal to the predetermined voltage, the charge current is negatively correlated with the first node point voltage or the second node point voltage.
 3. The wireless power system of claim 1, wherein the current mirror circuit comprises: a first transistor, comprising a first node, a second node, and a control node, wherein the first node of the first transistor is configured to receive the rectified voltage signal, and the second node of the first transistor couples with the third node point; and a second transistor, comprising a first node, a second node, and a control node, wherein the first node of the second transistor is configured to receive the rectified voltage signal, and the second node of the second transistor couples with the first node point; wherein the control node of the first transistor and the control node of the second transistor are configured to receive the mode switching signal.
 4. The wireless power system of claim 3, wherein the current mirror circuit further comprises: a regulating transistor, comprising a first node, a second node, and a control node, wherein the first node of the regulating transistor is coupled with the second node of the first transistor, and the second node of the regulating transistor is coupled with the third node point; and a regulating operational amplifier, comprising a first input node, a second input node, and an output node, wherein the first input node of the regulating operational amplifier is coupled with the first node of the regulating transistor, the second input node of the regulating operational amplifier is coupled with the first node point, and the output node of the regulating operational amplifier is coupled with the control node of the regulating transistor.
 5. The wireless power system of claim 1, wherein the active rectifier comprises: a fifth transistor, comprising a first node, a second node, and a control node, wherein the first node of the fifth transistor is configured to provide the rectified voltage signal, the second node of the fifth transistor is coupled with the first node of the secondary side coil through a fourth node point and configured to receive the input voltage signal; a sixth transistor, comprising a first node, a second node, and a control node, wherein the first node of the sixth transistor is configured to provide the rectified voltage signal, the control node of the sixth transistor is coupled with the second node of the fifth transistor, the second node of the sixth transistor is coupled with the control node of the fifth transistor, and coupled with a second node of the secondary side coil through a fifth node point; a seventh transistor, comprising a first node, a second node, and a control node, wherein the first node of the seventh transistor is coupled with the fourth node point, and the second node of the seventh transistor is coupled with the ground terminal; an eighth transistor, comprising a first node, a second node, and a control node, wherein the first node of the eighth transistor is coupled with the fifth node point, and the second node of the eighth transistor is coupled with the ground terminal; a first capacitor, comprising a first node, and a second node, wherein the first node of the first capacitor is configured to receive the rectified voltage signal, and the second node of the first capacitor is coupled with a sixth node point; a second capacitor, coupled between the sixth node point and the ground terminal; and a control circuit, coupled with the control node of the seventh transistor and the control node of the eighth transistor, configured to receive a fourth node point voltage from the fourth node point, and receive a fifth node point voltage from the fifth node point, wherein the control circuit is configured to control the seventh transistor and the eighth transistor according to the fourth node point voltage and the fifth node point voltage.
 6. The wireless power system of claim 5, wherein when the fourth node point voltage is lower than a ground voltage, the control circuit switches the seventh transistor from a switch-off state to a conducted state, and when the fifth node point voltage is lower than the ground voltage, the control circuit switches the eighth transistor from the switch-off state to the conducted state.
 7. The wireless power system of claim 5, wherein the control circuit comprises: a first comparator, comprising a first input node, a second input node, and an output node, wherein the first input node of the first comparator is coupled with the ground terminal, the second input node of the first comparator is coupled with the fourth node point, and the output node of the first comparator is coupled with the control node of the seventh transistor; and a second comparator, comprising a first input node, a second input node, and an output node, wherein the first input node of the second comparator is coupled with the ground terminal, the second input node of the second comparator is coupled with the fifth node point, and the output node of the second comparator is coupled with the control node of the eighth transistor.
 8. The wireless power system of claim 7, wherein the control circuit further comprises: a first adder, coupled with the second input node of the first comparator; a second adder, coupled with the second input node of the second comparator; and a compensation circuit, configured to output a first compensation signal and a second compensation signal to the first adder and the second adder, respectively; wherein when the seventh transistor is switched from a switch-off state to a conducted state, the first compensation signal has a first voltage level, and when the seventh transistor is switched from the conducted state to the switch-off state, the first compensation signal has a second voltage level; wherein when the eighth transistor is switched from the switch-off state to the conducted state, the second compensation signal has a third voltage level, and when the eighth transistor is switched from the conducted state to the switch-off state, the second compensation signal has a fourth voltage level; wherein the second voltage level is higher than the first voltage level, and the fourth voltage level is higher than the third voltage level.
 9. The wireless power system of claim 5, wherein the active rectifier further comprises: a ninth transistor, comprising a first node, a second node, and a control node, wherein the first node of the ninth transistor is coupled with the second node of the fifth transistor, and the second node of the ninth transistor is coupled with the fourth node point; a tenth transistor, comprising a first node, a second node, and a control node, wherein the first node of the tenth transistor is coupled with the second node of the sixth transistor, and the second node of the tenth transistor is coupled with the fifth node point; an eleventh transistor, comprising a first node, a second node, and a control node, wherein the first node of the eleventh transistor is coupled with the fourth node point, and the second node of the eleventh transistor is coupled with the first node of the seventh transistor; and a twelfth transistor, comprising a first node, a second node, and a control node, wherein the first node of the twelfth transistor is coupled with the fifth node point, the second node of the twelfth transistor is coupled with the first node of the eighth transistor, and the control node of the ninth transistor, the control node of the tenth transistor, the control node of the eleventh transistor, and the control node of the twelfth transistor are coupled with the sixth node point.
 10. The wireless power system of claim 1, wherein the buck converter comprises: a thirteenth transistor, comprising a first node, a second node, and a control node, wherein the first node of the thirteenth transistor is coupled with the first node point, the second node of the thirteenth transistor is coupled with a seventh node point, and the control node of the thirteenth transistor is configured to receive a first switch signal; a fourteenth transistor, comprising a first node, a second node, and a control node, wherein the first node of the fourteenth transistor is coupled with the seventh node point, the second node of the fourteenth transistor is coupled with the ground terminal, and the control node of the fourteenth transistor is configured to receive a second switch signal; an inductor, coupled between the seventh node point and an eighth node point; a fifteenth transistor, comprising a first node, a second node, and a control node, wherein the first node of the fifteenth transistor is coupled with the eighth node point, the second node of the fifteenth transistor is configured to provide the first output voltage signal, and the control node of the fifteenth transistor is configured to receive a third switch signal; a sixteenth transistor, comprising a first node, a second node, and a control node, wherein the first node of the sixteenth transistor is coupled with the eighth node point, the second node of the sixteenth transistor is configured to provide the second output voltage signal, and the control node of the sixteenth transistor is configured to receive a fourth switch signal; and a seventeenth transistor, comprising a first node, a second node, and a control node, wherein the first node of the seventeenth transistor is coupled with the eighth node point, the second node of the seventeenth transistor is coupled with the ground terminal, and the control node of the seventeenth transistor is configured to receive a fifth switch signal.
 11. The wireless power system of claim 10, wherein the buck converter further comprises: an eighteenth transistor, comprising a first node, a second node, and a control node, wherein the first node of the eighteenth transistor is coupled with the second node of the thirteenth transistor, and the second node of the eighteenth transistor is coupled with the seventh node point; and a nineteenth transistor, comprises a first node, a second node, and a control node, wherein the first node of the nineteenth transistor is coupled with the seventh node point, and the second node of the nineteenth transistor is coupled with the first node of the fourteenth transistor; wherein the control node of the eighteenth transistor and the control node of the nineteenth transistor are configured to receive a second reference voltage, and magnitude of the second reference voltage is half of magnitude of the first node point voltage. 